LUMBER GRADE MIX STUDY

Background:  Yorktowne, Inc. is a manufacturer of kitchen cabinets utilizing hard maple, red oak, cherry, and hickory.  The operation receives green hardwood lumber from various sawmills in the Northeastern United States then pre-dries, kiln dries, sorts, and surfaces the lumber in preparation for manufacturing.

Situation:  A recent market-driven shift from oak to hard maple as the primary species prompted Yorktowne management to investigate its present green lumber grade mix purchasing and cutting policies.  A complicating factor is the difference in the color of maple’s heartwood and sapwood.  Lumber grade rules admit unlimited sapwood and heartwood i.e., ‘color’ is not considered a defect that reduces grade.  Much of the hard maple product is sold in clear or lightly stained finishes.  These products require dimension parts cut primarily from the light-colored sapwood rather than the darker heartwood.  A conceptual plan was outlined to optimize the lumber grade mix with consideration in the color of hard maple’s heartwood and sapwood. 

Yorktowne, Inc. then engaged A. G. Raymond & Company to analyze and select the optimum grade mixes for each species. 

The initial step in the data collection/simulation phase was establishing the procedures used on the gang rip first line operation.  Rough lumber dimensions, type of gang rip saw, arbor spacing, number of different lengths open at the optimizing saw, kerfs, size of end trims, salvage specifications, and prioritization strategies were collected and entered into a software simulation package developed by the USDA – Forest Service.  A variety of grade mixes were simulated outputting a theoretical yield and gross board footage requirement.  These data were then used to calculate the direct material and labor costs. 

After all potential grade mixes were identified, an on-site yield test was performed to validate the yields generated from the simulation software and to determine the expected ratio of sapwood and heartwood in each grade mix.  Lumber was tallied and recorded according to current operation procedures at the in-feed of the gang rip saw, the out-feed of the optimizing saws, the matching saws, the moulders, and the inspection stations for each grade mix. 

Capacities for all rough mill process centers were calculated and compared to the projected gross board footage requirements to ensure demands could be met.  The grade mix with the least cost per net board foot was then identified for each species. 

In December 2000, three months after the completion of the lumber grade mix study, all recommended grade mixes were implemented and projected yields were being obtained.